In recent years, a fuel cell capable of operating even at room temperature and obtaining a high output density has attracted attention as a power supply for an electric vehicle and a stationary power supply in response to social demand and trend against a backdrop of energy/environmental problems. In the fuel cell, a product generated by an electrode reaction is water in theory, and the fuel cell is a clean power generation system that hardly affects the terrestrial environment. In particular, a polymer electrolyte fuel cell operates at a relatively low temperature, and accordingly, has been expected as the power supply for the electric vehicle.
In general, the polymer electrolyte fuel cell includes a single cell in which a membrane electrode assembly (MEA) is sandwiched between separators on which gas flow passages and the like are formed. The electrolyte membrane-electrode assembly is one formed by disposing electrodes having catalyst layers and gas diffusion layers on both surfaces of a polymer electrolyte membrane. Ends of the electrolyte membrane in a surface direction protrude from ends of the electrodes in the surface direction to the outside. And, on such protrusions of the electrolyte membrane, gasket layers having a gas sealing function are provided in order to prevent gas leakage to the electrodes opposite thereto or gas leakage to the outside.
In the conventional polymer electrolyte fuel cell, in some case, a clearance has occurred between each of the separators and each of the gasket layers, and fuel or oxidant gas has leaked therefrom, whereby performance of the fuel cell has been decreased, and intimate contact property between each of the separators and each of the electrodes cannot be ensured sufficiently, resulting in that desired power generation characteristics are not exerted. In this connection, in Japanese Patent Unexamined Publication No. 2002-324556, there has been disclosed a single cell in which an electrolyte membrane-electrode assembly having gasket layers is sandwiched by separators, wherein a thickness of the gasket layers before being sandwiched by the separators is made thinner than a thickness of electrodes.